In German Patent Document DE-A 19627055, a method of lubricating a plurality of lubrication sites or locations is effected by providing individual lubricant dispensers at these sites and equipping each dispenser with an electric motor drive, a controller, a lubricant container holding a supply of the lubricant and a spindle connected to the drive and to the piston so that, upon rotation of the spindle, the piston presses the lubricant out of the dispenser to the site to be lubricated.
The control device can be connected to a central controller and the quantity of lubricant dispensed from the dispenser is thereby controlled by the central unit. The lubricant controller transmits signals to the central unit representing the piston position so that, at the central unit, information as to the state of filling of the lubricant dispenser can be read. The control software required for this purpose can be expensive, complex and difficult to create, especially if a large number of lubricant sites are provided with individual needs as to lubrication and different quantities of lubricant.
The lubricant dispensers can be equipped with motion sensors whose signals are transmitted to the central unit for signal processing there and, upon replacement of a lubricant dispenser, old data must be erased at the central unit and start up data for the new unit must be programmed into the central unit. Since this may result in extensive manual programming, the danger of operator error is relatively high.
The central unit also controls the lubricant dispensers by triggering them at predetermined time intervals. When the entire system operates more or less continuously, this approach affords sufficient accuracy. However, should there be interruptions in operation or continuous operation is not possible, there is a danger that the lubricant will be improperly metered to the particular site since then the lubrication pulses may not be sufficiently synchronized to the actual operating time of the machine to be lubricated.